The present invention relates generally to mining and specifically to conveying in remote mining of bedded mineral deposits.
Known methods of remote mining in bedded mineral deposits such as coal seams employ a mining machine that excavates mine openings to some distance from the seam exposure on the surface and means of conveying are required to transport the excavated material to the surface. In most of the present systems, conveying machines consisting of multiple conveyors are advanced into the mine openings from the surface. For example, U.S. Pat. Nos. 5,112,111, 5,232,269 and 5,261,729 to Addington at al. disclose an assembly of conveyors and a mining machine advanced into the seam without interrupting the flow of aggregate material by separate means designed to pull at the forward end and push at the rearward end. Similarly, U.S. Pat. No. 5,609,397 to Marshall at al. discloses an assembly of conveyors interconnected with a mining machine and a driving device located outside the seam and consisting of rack and pinion or, alternately, reciprocating cylinders, linear tracks, linear or rotary drives, chains, cables or other mechanical devices. The U.S. Pat. No. 5,692,807 to Zimmerman discloses a guidance assembly for extending and retracting an assembly of conveyors in and out of the seam. The U.S. Pat. No. 3,497,055 to Oslakovic at al. discloses a multi-unit train of conveyors having a self-propelled unit at each end coupled to intermediate units, each end unit being capable of towing the intermediate units. The U.S. Pat. No. 2,826,402 to Alspaugh at al. discloses a train of wheeled conveyor sections pulled into the mine opening and pushed out of it by a self-propelled mining machine. Buckling of the train is avoided by the grooves made by the mining machine in the floor, said grooves spaced the same distance as the treads of the wheels carrying the conveyor sections.
At present, as the interconnected combination of the mining machine and a conveying assembly comprising a plurality of conveyors is advanced some distance into the seam from a launch vehicle located on the outside, the axial force within the combination becomes excessive with respect to its length and the combination becomes less rigid. As a consequence, it becomes difficult to steer the mining machine located at the front of the combination and the conveying assembly itself can become unstable, which limits the penetration depth of mining. Furthermore, pulling the conveying assembly at the rearward end when it becomes entrapped by a rock fall may sometimes cause the conveying assembly to brake. It would therefore be desirable to provide for advancing and withdrawing the conveying assembly while minimizing the axial force within the conveying assembly.
Where the conveying assembly consists of a plurality of conveyor units, each of the individual conveyors requires a separate input of electric power which, in turn, requires coupling and uncoupling of electrical cables as the assembly is advanced into or retracted from the mine opening. It would be therefore desirable to provide a power input that does not require electric power at each individual conveyor of the assembly.
If the electric power input is not provided at each individual conveyor, the conveying assembly cannot be extended without interruption, as claimed in the U.S. Pat. No. 5,112,111 to Addington at al. It would therefore be desirable to provide for extending the conveying assembly while minimizing the time required for such extension of the machine.
Where open conveyors are used, they are prone to damage by falls of rock from unsupported roof. Often, when rock falls occur, mining must be interrupted and the conveying assembly brought to the surface in order to remove fallen rock from the machine and to repair damage. It would therefore be desirable to provide a conveying assembly that is enclosed in a protective enclosure and that is capable of withstanding at least moderate rock falls.
Electric cables, control cables and hoses for the remote mining machine that lay atop the conveying assembly are also prone to damage by rock falls. It would therefore be desirable to provide protective enclosures for cables, hoses and other services provided for the remote mining machine.
A remote mining machine located at the forward end of the conveying assembly may become entrapped by fallen rock and the traction force of the conveying assembly may not be sufficient to extract the mining machine. It would therefore be desirable to provide independent means of extracting the mining machine from the seam.
One type of mining for which the present invention is intended to be used is highwall mining. With highwall mining, the mining machine penetrates a substantially vertical face containing a seam. The mining machine digs into the face substantially perpendicularly thereto. To ensure the structural integrity of the mine is maintained, pillars of unmined material are left between the holes dug by the mining machine. These pillars support the roof and are therefore essential to avoiding a rock fall. Those of ordinary skill in the art will understand that in order to maintain minimum acceptable pillar thickness, it is desirable to dig exactly perpendicularly to the face. Any angular deviation by the mining machine as it travels requires an increased initial pillar width, which decreases the amount of material that can be removed from the mine. Therefore it is desirable to maintain accurate and precise knowledge of where the mining machine is located. Likewise, it is desirable to navigate the mining machine precisely and accurately to a desired location. In this manner, the operator can ensure that the desired mining path is followed.
One known method of determining mining machine position employs a system of gyros and accelerometers to estimate the distance traveled by the mining machine. This type of known method uses complicated software that requires several minutes to initiate during which the mining machine cannot be moved. The method also requires periodic re-calibration during use, which also requires the mining machine be at rest. Furthermore, this system is expensive, costing more than $100,000. Thus, what is needed is a cost-efficient mining machine that can accurately and precisely determine the position of the mining machine head.
Accordingly, it is an object of the present invention to provide a method and apparatus for advancing a remote conveying assembly without causing excessive axial forces within the assembly, by providing tractive forces at multiple locations along the length of the assembly.
Another object of the present invention is to provide a method and apparatus for remote conveying that does not require electric power at each conveying section of the conveying assembly.
Another object of the present invention is to provide a method and apparatus for extending the conveying assembly that minimizes the time required for extensions.
Another object of the present invention is to provide a method and apparatus for protecting the remote conveying assembly, electric cables and other services from damage by rock falls.
Another object of the present invention is to provide a method and apparatus for advancing and steering the remote mining machine independently of advancing the conveying assembly.
Another object of the present invention is to provide a method and apparatus for accurately and precisely determining the position of the mining machine within the seam.
These and other objects of the present invention will become clear from the detailed description of the invention, the drawings, and the claims included below.